I've had a few java fern and some driftwood develop hair algae in my tank.


I've the same problem on my larger / older leaves. I was told by the
LFS that the dark fur algae is common for Ferns. Otos will eat a
little bit of it.

One thing to look out for is "liquid plant food".

I doubled my light output a few weeks ago and thought "I should start
using liquid iron supplements". Once I put a capful in, I got algae.

Now I use root tabs only.